Anterior cervical discectomy and fusion (ACDF) is a common type of neck surgery that involves removing a damaged disc to relieve pressure on the spinal cord or nerve root and thereby alleviate associated pain, numbness, weakness or tingling. The damaged disc is removed from between two vertebral bones along with simultaneous fusion surgery. The fusion involves placing a bone graft or “cage” and/or implants where the disc was originally located to stabilize and strengthen the area.
The use of cages for ACDF are important postoperatively to the alignment of the cervical spine and to maintain the intervertebral disc height. Few studies, however, have examined the impact of the underlying cancellous or “spongy” bone contact with regards to handling large loads from the cage. Moreover, it is still not clear whether a cage with or without screws will be the best choice for long-term fusion as the micromotion or sliding distance and subsidence or penetration of the cage still take place repeatedly.
Researchers from Florida Atlantic University’s College of Engineering and Computer Science, in collaboration with Frank Vrionis, M.D., senior author of the study and director of the Marcus Neuroscience Institute, part of Baptist Health; and professor of surgery, FAU’s Schmidt College of Medicine, are the first to evaluate the effect of the range of motion, cage migration and subsidence using variable angle screws. Marcus Neuroscience Institute has its hub on Boca Raton Regional Hospital’s campus and satellite locations at Bethesda Hospital in Boynton Beach and Deerfield Beach.
For the study, researchers developed five finite element models from a cervical spine model. The first model was an intact spine model, and the second model was an altered model with cage insertion and a 2-level static plate. The other three models were altered models with the same cage insertion and a 2-level dynamic plate. They compared ACDF cages with and without screws on the biomechanical characteristics of the human spine, implanted cage, and associated hardware by comparing the micro motion and subsidence.
Results of the study, published in The Spine Journal, the journal World Neurosurgery and Asian Spine Journal showed that the cage-screw and anterior plating combination model has promising potential to reduce the risk of micro motion and subsidence of implanted cages in two or more level ACDFs. This method could increase the stiffness of the construct and reduce the incidence of clinical and fusion failure following ACDF, which in turn, could decrease the need for revision surgeries or supplemental posterior realignment.
“Anterior cervical discectomy and fusion is widely used to treat patients with spinal disorders, where the cage is a critical component to achieve satisfactory fusion results. The risk factors for cage migration are multifactorial and include patient factors, radiological characteristics, surgical techniques and postoperative factors,” said Vrionis. “Our results showed that the plate used in our study provided directional stability and obtained excellent fusion, indicating promising clinical outcomes for patients with degenerative cervical spine disease.”
Vrionis further explains that because of the biomechanical stability of the current construct, there has been no need for a rigid cervical collar, which is typically used by other surgeons.
“In addition, with more than 100 clinical cases, there has been no evidence of pseudarthrosis or lack of fusion, which is a treated complication of anterior cervical disc surgery,” said Vrionis.
A lower screw rotational angle resulted in superior biomechanical performance and lower incidence of migration and subsidence compared with a higher rotational angle in multilevel applications, regardless of loading. The researchers believe the underlying mechanism may be due to the cage-screw bonded to the bone and the constrained bottom of C5 vertebra making it more rigid.
“Our research aims to develop a platform for next generation patient-specific spine surgery by combining intelligent image process, AI technology/machine learning, finite element simulation and 3D printing to help surgeons design a surgery plan for each patient, ” Chi-Tay Tsai, Ph.D., study co-author and a professor, FAU Department of Ocean and Mechanical Engineering, and director, FAU Spine Biomechanical Laboratory.
Researchers demonstrated that the cage-screw was able to prevent subsidence in all loading scenarios better than the cage without screws.
“Our clinical and biomechanical data have shown that the outcomes with the rigid static plate are very good. The main reason may be due to greater contact area between the cortical and cancellous bone in the cage-screw than that in unanchored cage constructs,” said Tsai.
ACDF is one of the most commonly performed spinal operations in the United States with an average of 137,000 procedures performed each year.
“The novel methodology developed by our researchers in collaboration with Drs. Vrionis and O’Connor of the Marcus Neuroscience Institute holds great promise to enhance anterior cervical discectomy and fusion and ultimately help to alleviate the pain and discomfort patients experience from various disorders of the spine and neck,” said Stella Batalama, Ph.D., dean, FAU College of Engineering and Computer Science.
Other study co-authors are Erik Engeberg, Ph.D., professor, FAU Department of Ocean and Mechanical Engineering; Maohua Lin, Ph.D., research scientist, FAU Department of Ocean and Mechanical Engineering; Stephen Z. Shapiro, M.D., a neurosurgery resident at Louisiana State University; and James Doulgeris, Ph.D., both at the Department of Neurosurgery, Marcus Neuroscience Institute, Boca Raton Regional Hospital, part of Baptist Health; Rudy Paul, Ph.D., FAU Department of Ocean and Mechanical Engineering; and Timothy E. O’Connor, Ph.D., Department of Neurosurgery, Marcus Neuroscience Institute.
The research was funded by the Boca Raton Regional Hospital Foundation awarded to Tsai, principal investigator.
– FAU –
About FAU’s College of Engineering and Computer Science:
The FAU College of Engineering and Computer Science is internationally recognized for cutting edge research and education in the areas of computer science and artificial intelligence (AI), computer engineering, electrical engineering, biomedical engineering, civil, environmental and geomatics engineering, mechanical engineering, and ocean engineering. Research conducted by the faculty and their teams expose students to technology innovations that push the current state-of-the art of the disciplines. The College research efforts are supported by the National Science Foundation (NSF), the National Institutes of Health (NIH), the Department of Defense (DOD), the Department of Transportation (DOT), the Department of Education (DOEd), the State of Florida, and industry. The FAU College of Engineering and Computer Science offers degrees with a modern twist that bear specializations in areas of national priority such as AI, cybersecurity, internet-of-things, transportation and supply chain management, and data science. New degree programs include Master of Science in AI (first in Florida), Master of Science and Bachelor in Data Science and Analytics, and the new Professional Master of Science and Ph.D. in computer science for working professionals. For more information about the College, please visit eng.fau.edu.
About Florida Atlantic University: Florida Atlantic University, established in 1961, officially opened its doors in 1964 as the fifth public university in Florida. Today, the University serves more than 30,000 undergraduate and graduate students across six campuses located along the southeast Florida coast. In recent years, the University has doubled its research expenditures and outpaced its peers in student achievement rates. Through the coexistence of access and excellence, FAU embodies an innovative model where traditional achievement gaps vanish. FAU is designated a Hispanic-serving institution, ranked as a top public university by U.S. News & World Report and a High Research Activity institution by the Carnegie Foundation for the Advancement of Teaching. For more information, visit www.fau.edu.
About Marcus Neuroscience Institute:
Marcus Neuroscience Institute, a part of Baptist Health South Florida, is an innovative nexus for neurologic and neurosurgical care. From non-surgical treatments and minimally invasive procedures to complex brain and spine surgery, the Institute embraces a multidisciplinary approach to patient care. Marcus Neuroscience Institute’s highly skilled staff is comprised of neurosurgeons, neurologists, pain management physicians and neuro-oncologists. With locations in Boca Raton, Boynton Beach and Deerfield Beach, Marcus Neuroscience Institute is making breakthrough neurological care more accessible for patients seeking comprehensive treatment for conditions affecting the brain, spine and peripheral nervous system.
The heart of the Institute is located at Boca Raton Regional Hospital. The 66,000-square-foot facility houses a 20-bed Neuro Intensive Care and Step-Down Unit, four dedicated operating rooms — including one equipped with intraoperative MRI and two with intraoperative CT capability — and a biplane angiography suite, a crucial component in the diagnosis and care of neurological conditions.
Marcus Neuroscience Institute is training the next generation of neurologists and neuroscientists in conjunction with Florida Atlantic University’s Charles E. Schmidt College of Medicine and its residency program. The Institute earned the Gold Seal of Approval® for Spinal Surgery Certification from The Joint Commission, which reflects commitment to the highest standards of excellence and safety in patient care, and the Institute is a DNV Certified Comprehensive Stroke Center, which is the nation’s highest level of stroke accreditation. For more information, visit: BRRH.com/MarcusNeuroscienceInstitute.
